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Title page for ETD etd-12032009-110833

Type of Document

Dissertation

Author

Cohen, Jeremiah Yaacov

Author's Email Address

jeremiah.cohen@gmail.com

URN

etd-12032009-110833

Title

Neural coding and timing of visual target selection in the frontal eye field

Degree

PhD

Department

Neuroscience

Advisory Committee

Advisor Name

Title

Mark T. Wallace

Committee Chair

Jeffrey D. Schall

Committee Member

Martin Paré

Committee Member

René Marois

Committee Member

Keywords

visual search

decision making

target selection

frontal eye field

Date of Defense

2009-11-30

Availability

unrestricted

Abstract

How does the brain select visual targets for eye movements? We recorded neural activity while macaques performed visual search in which they were trained to move their eyes to a target stimulus among an array of distractor stimuli for a reward. Three signals were used to measure the relationship between the decision to move the eyes to a target and neural activity: spike rates from neurons in the frontal eye field (FEF), local field potentials from FEF, and event-related potentials recorded from the skull. We found that (1) FEF neurons cooperated and competed to select visual targets, measured using correlations between spike times of simultaneously recorded neurons, (2) FEF neurons interacted more when the visual search task was easier (i.e., the target and distractors were easily discriminable), measured using a multivariate analysis and decreased firing variability before eye movements, (3) FEF neurons decreased firing variability around the time of target selection by the mean firing rate, (4) FEF neurons were distinguished both functionally and biophysically, on the basis of action potential width, (5) FEF selected search targets from distractors before the macaque homologue of a human cognitive event-related potential (the N2pc) that marks the allocation of attention, and (6) the time between visual search array presentation and the time that FEF neurons discriminated between target and distractors was later when there were more stimuli the animal needed to choose from.